Incinerator

ABSTRACT

An incinerator particularly suitable for in-house under-counter installation and use comprising a well heat-insulated structure including combustion or trash chamber and a second or afterburner chamber divided into two volumes, one being a volatiles combustion chamber containing the burner and the other being an exhaust flue, and recirculating means whereby combustion products and smoke are directed out of the combustion chamber through the burner flame for incineration. Included also is a novel air flow system for providing circulating air for combustion simultaneously with jacket cooling, means for delaying the combustion process until the afterburner has become sufficiently preheated, and means for providing automatic combustion rate control whereby rate of combustion is automatically kept constant despite large variations in the type, heat content, and size of the charge being incinerated.

Dec. 4, 1973 ABSTRACT and means for providing auto- Primary Examiner1(enneth W. Sprague Attorney-Harold A. Murphy et al.

An incinerator particularly suitable for in-house under-counter installation and use comprising a well heat-insulated structure including combustion or trash chamber and a second or afterbumer chamber divided into two volumes, one being a volatiles combustion chamber containing the burner and the other being an exhaust flue, and recirculating means whereby combustion products and smoke are directed out of the combustion chamber through the bumer flame for incineration. Included also is a novel air flow system for providing circulating air for combustion simultaneously with jacket cooling, means for delaying the combustion process until the afterbumer has become sufficiently preheated matic combustion rate control whereby rate of combustion is automatically kept constant despite large variations in the type, heat content, and size of the charge being incinerated.

21 Claims, 5 Drawing Figures 110/8 A, 110/49 R F23g 5/00 110/8 R, 8 A, 110/18 R, 18 C Robert D. Di Nozzi, Dedham, both of Mass.

Mass.

Filed: June 2, 1972 [21] Appl. No.: 259,324

References Cited UNITED STATES PATENTS 7/1956 6/1970 Maitilasso... 11/1957 B0uchard.... 1l/1970 Lausmann...

I Umted States Patent Hapgood et al.

[ INCINERATOR [75] Inventors: William H. Hapgood, Brookline;

[73] Assignee: Raytheon Company, Lexington,

[52] US. [51] Int. [58] Field of PMENTEU 0m 4 4915 SHEET 10? 3 PATENTEUDEB' 4197s SHEET 2 BF 3 INCINERATOR BACKGROUND OF THE INVENTION Incinerators designed for use in the home generally have been intended for use in a basement or like area such as a furnace room, usually an area where ready connection may be made into a chimney. In such incinerators generally no great effort has been devoted to the production of extremely efficient combustion of trash products with little residue, or to creation of efficient jacket cooling such as would allow the incinerator to be incorporated safely in the counter space in the kitchen as a built-in appliance.

In some known types of incinerators, considerable expense and complexity is involved in providing a trash chamber and an afterburner chamber with separate individual burners which necessitate separate fuel supply systems and controls.

In certain other incinerators combustion is prolonged and incomplete due to the fact that the systems are designed to commence combustion before the afterbumer has been sufficiently preheated, thus producing undesirable smoke pollution during at least the early stages of the combustion process.

SUMMARY OF THE INVENTION The above and other objections to known incinerators are overcome or improved upon by the present invention wherein a novel incinerator is provided which .has a single air circulation system providing efficiently both cool air for jacket cooling and for combustion. The invention relates to an incinerator of the recirculating type wherein a single burner is located in an afterburner and is operated in a controlled manner to provide preheating of the afterbumer to a controlled level prior to providing circulation into the trash chamber for burning of the contents therein. This is accomplished by means for keeping the air injection at a very low level for a controlled initial period such as 6' to 8 minutes, for example, thereby stalling combustion of the charge in the trash chamber until the afterbumer temperatures reach predetermined levels.

The invention also includes a feedback system whereby combustion-rate control is accomplished so that added volume of combustion products or, more particularly, increase in the volume or pressure of gases generated by combustion, pyrolization, or vaporization will cause a proportionate decrease in input air flow, thus maintaining a substantially constant combustion rate. This is achieved by providing properly located communicating ports between the trash chamberand the afterbumer, together with a novel pumping system for input air. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a diagram illustrating circulation in the incinerator of FIG. 1; and

FIG. 5 is a diagram of the incinerator air flow.

DESCRIPTIQNOF THE PREFERRED EMBODIMENTS Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the several views, there is shown in FIG. 1 an incinerator embodying the present invention. This incinerator, indicated generally by numeral .10, is intended primarily for use in a kitchen as an appliance built into a counter. However, it will be understood that the features of the invention may be applied to other incinerators such as, for example, commercial or industrial types.

The incinerator 10 is enclosed within an outer shell or-jacket 12, preferably metal, all four walls and top of which are spaced from the incinerator by a space 14 through which air can pass for cooling purposes, as will be described. The bottom of the incinerator may be supported as by legs on a base 16, for example, whereby the air flow space is continued beneath the incinerator.

Thelincinerator 10 is of the recirculating type which comprises a trash chamber 18 in which the charge to be incinerated is deposited through a door 20. Adjacent trash chamber 18 is an afterbumer 22 (FIGS. 2 and 3) which is divided by a vertically extending plate 24into two regions, a volatiles combustion chamber 26 and an exhaust flue 28. Plate 24 extends'at its upper end all the way to the top wall of the incinerator. However, its lower end terminates short of the bottom wall of the incinerator, as shown in FIG. 2, to provide communication between the chamber 26 and the flue 28. It will be apparent, however, that other means may be provided for such communication if desired, such as by extending plate 24 all the way to thebottom of the incinerator and providing it with one or more openings or ports for communication between the two regions, for example. The wall 30 between the trash chamber 18 and the afterbumer 22 is provided with two ports or orifices, one port 32 being located near the upper end of the wall and the other port 34 being located near the bottom of the wall. The'ports 32 and 34, each of which individually comprise single or multiple orifices, thus provide for communication between both the upper and lower portions of the trash chamber and afterburner.

The walls of the incinerator 10 are made of heat insulatingmaterial 36 and the inner surface is linedwith metal 38. Wall or partition 30 and divider 24 are also 46 which coaxially encircles the exhaust pipe 42 in spaced relation with it. A vertical baffle 48 in box 44 divides the interior of the box into two compartments 50 and 52. Exhaust pipe 42 terminates within compartment 52 and has an uppervent'54 whereby exhaust products will pass from pipe 42 into compartment 52 and then out through vents 56 in the box. Additional vents 58 in the box provide means whereby fresh cool air may flow into compartment 50 and then through the annular space between pipes 46 and 42 into the space between the incinerator and jacket 12.

The volatiles combustion chamber 26 in the afterburner 22 is designed to burn up all smoke, odor and other combustion products coming from the trash chamber 18. It does this by means of a high-input, hot, turbulent flame generated in a tortuous insulated chamber. The flame is produced by a burner 60 of a fluid-fueled or electric type. The burner 60 is illustrated diagrammatically in FIGS. 1 and 3 as a gasfueled unit mounted in one side wall of the chamber 26 near the top thereof. Burner 60 is supplied with fuel through piping 62 via a regulator valve 64 from any suitable source (not shown). The burner 60 may take any one of the several forms which are well known, either electrical or gas-fueled, and, therefore, is not described in further detail herein. If gas-fueled, the burner may be ignited by any suitable means such as a sparking device 61. Air for the burner 60 is supplied through tube 66 from a plenum chamber or manifold 68 which is connected to a volute 70 having the usual motor 72 and fan (not shown) which thus fonns a pump. The chamber 68, volute'70 and motor 72 are mounted on the outside of the incinerator 10 between it and the jacket 12 so that air will be drawn in through tube 46 and compartment 50 in box 44. The incoming air is drawn through tube 46 around tube 42 and cools the jacket 12 by flowing through space 14.

For providing a controlled jet stream of air for circulation through the incinerator chambers, there is provided a piping 74 which has one end connected to the plenum chamber 66 and its other end extending into the trash chamber 18 and terminating adjacent one end of a conduit 76 which is mounted at its other end in upper port 32. The inner end of pipe 74 has a nozzle 78 which is located adjacent the end of conduit 76, as shown in FIG. 2, and which is smaller in diameter than the inside of the conduit so that air may be injected directly from the nozzle into the conduit while circulation air and combusion products from the trash chamber will simultaneously flow into the conduit around the nozzlefThis feature provides controlled oxygen levels and will be described more fully hereinafter.

To complete the air circulation system, air within the volatiles combustion chamber 26 will recirculate back into the trash chamber through a conduit 80 which is located within the lower port 34.

The door is an assembled structure which includes an inner insulated closure panel 82 which interfits within an opening in the incinerator wall 36-38. The outer exposed door panel 84 is located substantially flush with the adjacent jacket wall and connected in spaced relation to panel 82 by bolts so that an insulating air space is provided between the panels. The door assembly 20 is hinged to the jacket and provided with a suitable handle for manual operation.

It has been found in operation of this apparatus that when the burner 60 is operated simultaneously with blower 72, hot burner gases are directed downwardly within the volatiles combustion chamber 26, through the open space 86 beneath dividing wall 24 into the flue 28, and also simultaneously some thereof are directed back into the trash chamber in a recirculating pattern through lower ports 34 and 32. All gases from the trash chamber 18 pass through upper port 32 into the afterburner and mix with the burner flame, effecting com- "plete combustion of smoke and odors. As described above, part of this mixture of combusted gases passes through the lower port 34 back to the trash chamber and becomes the source of heat by means of which the trash is heated and burned. Thus, only a single burner is required for the incinerator.

The porting arrangementdescribed allows the trash 'or combustion chamber 18 to be rapidly heated up at the beginning of a cycle without initial combustion of trash until the afterburner has warmed up to the desired operating level, as will be described hereinafter.

Referring to FIG. 4, there is shown a diagram which illustrates air flow in the presently described device. All air to be used in the system enters through vent box 44 .and, as described, passes into the space 14 between the jacket 12 and the incinerator 10 where it is drawn into the blower 72. From the blower the air is split into three separate streams, one stream being directed to the burner 60 for mixing with the fuel in the formation of a flame, a second stream being directed through pipe .74 and noule 78 into upper port 32 where it is mixed chamber 18. Air from the afterburner 22 passes into the vent box outlet 52, and recirculation occurs between the afterbumer 22 and combustion chamber 18.

In further accordance with this invention, the described incinerator is provided with automatic combustion rate control, that is, a feedback control system whereby the rate of combustion is automatically kept fairly constant despite large variations in the type, heat content, and size of the charge. Such control is achieved without the use of any moving parts by the use p of properties of the combustion process itself.

Referring to FIG. 5, the combustionjrate control of this invention is diagrammatically illustrated. The incinerator comprises three chambers, one of which is the trash or combustion chamber 18 of approximately 2 cubic feet, for example, for the charge. The afterburner 22 includes the other two chambers, one of which is the volatiles combustion chamber 26 in which the burner flame, the smoke and other combustion products from the charge, and air are mixed and burned, and the flue 28 which is a final passive chamber for final burnout of smoke particulate matter.

The feedback control system of the iinvention includes the trash chamber 18 and the volatiles combustion chamber 26 which are therrnallyinsulated from each other except at the two ports 3 2 and 34. The structure of the pipes or conduits 78 and 76 in the upper port 32 forms a venturi pump which is a jet pump operated by low temperature, medium pressure air from the blower 72. Its function is to pump a constant volume of gas from the trash chamber 18 to the volatiles combustion chamber 26. i

The driving air supply mixes with the smoke and other combustion products rising from the trash chamber and is the excess air supply used for combustion of these products in the volatiles combustion chamber 26. The driving air supply and the pumped gas supply are approximately the same quantity, such as about six to eight cubic feet per minute, for example, and therefore a substantial pressure rise can be achieved in the jet pump. For example, with a 2-inch water column pressure available for the driving air, a pressure rise of 1/10 inch water column is easily achievable.

The mixture of combustion products from the trash chamber 18 and air from the pump 76 passes to the volatiles combustion chamber 26 where the burner adds sufficient heat to bring it to ignition temperature. The combustion products burn in this chamber 26, resulting in an additional temperature rise.

The lower port or ports 34 allows the hot gas from the volatiles combustion chamber to enter the trash chamber, bringing oxygen, heat, and a source of ignition to the trash.

When combustion is occurring in the trash chamber gases are given off. If combustion is complete in the trash chamber, then hydrocarbons are burning to water vapor and carbon dioxide. Often, due to excess of fuel, combustion will notbe complete in the trash chamber, and carbon monoxide, hydrocarbons, aldehydes, organic acids and other volatile products of partial combustion or thermal cracking will be driven off. These processes are accompanied by the liberation of heat in varying amounts.

The feedback of this invention is-accomplished in two stages. A constant volume of smoke and volatiles is fed to the volatiles combustion chamber and this puts an upper limit on the amount of combustion and heat release which will occur in the volatiles combustion chamber. More important, however, is the fact that as the rate of volatiles generation in the trash chamber increases, the pumping rate of the jet pump remains con-.

stant. Therefore, the flow rate of gases through the lower recirculation ports back into the trash chamber must decrease. In other words, the total'volume flow into the trash chamber equals the flow out, minus the internal volume generation. As the input decreases, so does the supply of both oxygen and heat. The limitation of oxygen limits the combustion rate, and the limitation of heat limits the volatilization rate of materials such as plastics and oils.

Control of both heat and oxygen is important. Oxygen must be controlled since oxygen can result in combustion and, with it, output of both heat and smoke. Heat must be controlled because, even in the absence of oxygen, heat will result in cracking, thermal decomposition, and volatilization of many organic compounds. This is the reason for the thermal insulation 30 between the trash chamber 18 and the volatiles combustion chamber 26. It limits the inputs which are required for combustion to the one source, the recirculation ports 32 and 34, and allows complete control by controlling the flow through these ports. This flow is automatically controlled by sensing the gas generation rate in the trash chamber, and decreasing the input flow through the recirculation ports whenever the vapor generation rate increases. The consequence is that the amount of smoke passing to the afterb'umer is held below a maximum for which the volatiles combustion chamber 26 is designed.

The second aspect of the feedback control depends on the temperature rise which occurs during combustion. As combustion rates increase, the temperature of the gases leaving the trash chamber ineases. As this hot smoke burns in the volatiles combustion chamber 26,

an additional temperature rise occurs. The gases presented to the recirculation ports are hotter during periods of burning, and a lower'mass flow rate will result through the recirculation ports. The result of this is an increase in the heat input to the trash, but a decrease in the oxygen input. As smoke combustion increases in the volatiles combustion chamber, the oxygen level naturally lowers so that a smaller mass of gas which is lower in oxygen content flows to the trash chamber 18. These effects are additive to the effect of decreased flow into the ports, so that the amount of oxygen available for trash combustion can easily decrease by an order of magnitude during a period of maximum burning. This is sufficient control to limit smoke generation to a rate which a smallvolatiles combustion chamber can handle, and also to limit heat generation to a level which will not damage the incinerator components.

It has been also that the up-start time in an incinerator cycle is the most critical time period in terms of smoke production. This is for the most part due to the smoke burning chamber 28 being initially too cool to adequately handle the smoke produced, this smoke being of greatest magnitude in the few minutes following the initial ignition of the charge.

In the presently described incinerator, heat is applied directly to the afterburner chamber 26 by a power burner and delivered to the trash chamber 18 via recirculation. The invention utilizes a constant displacement pump/air injection system to control recirculation, and hence combustion rate, as has been described.

To reduce the amount of smoke normally produced inthe first few minutes of incineration, this invention also includes a delay in the ignition of the charge until the afterburner has been sufficiently preheated. This is done by delaying recirculation by keeping air injection at a very low level for the predetermined initial time period. Low level air injection, as opposed to no air, prevents a reverse recirculation from occurring which could prematurely ignite the charge. This initial period will be on the order of 6 to 8 minutes. At this time the temperatures in the upper portion of the volatiles combustion chamber 26 will be about 2000 F and in the upper portion of the flue or exhaust chamber will be about 1400 F. During this initial period air injection through venturi 76 will be only about one or two cubic feet per minute, after which it will be increased to six to eight cfm.

The means by which the air injection is initially reduced to a low level may take any of several forms. For example, the entire incinerator is operated in controlled time cycles by means of a conventional timer (FIG. 1) which is operatively connected with the blower 72, the gas valve 64, and with a solenoidoperated valve in the pipe 74, as indicated by dash lines. The timer may also be connected to door locking mechanism (not shown). Therefore, the valve 90 may be operated by the timer to reduce input air flow during the initial controlled time period, and to increase input air flow to normal operating levels at the conclusion of the initial time period.

From the foregoing it will be apparent that a novel and efficient incinerator has been made in accordance with the objectives of this invention. It is also apparent, however, that various modifications and changes in the structure shown and described may be made by those skilled in the art without departing from the spirit of the invention as expressed in the accompanying claims. Therefore, all matter shown and described is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. An incinerator comprising an insulated housing containing trash and afterburner chambers, a wall between said chambers, port means in said wall, and pump means having a portion located in one chamber for causing inspiration of gases therefrom through the port means into the other chamber and thence back into said one chamber through the port means.

2. An incinerator comprising an insulated housing containing trash and afterburner chambers, a wall between said chambers, spaced first and second ports in said wall, and pump means having a portionlocated in said trash chamber adjacent said first port for introducing air under pressure through said first port and causing combustion products generated in the trash chamber to flow by inspiration therewith through the first port into the other chamber and thence back into said trash chamber through the second port.

3. An incinerator as set forth in claim 2 wherein a burner is located at least partially within the afterburner chamber.

4. An incinerator as set forth in claim 2 wherein said pump means is located in the trash chamber adjacent said first port.

5. An incinerator as set forth in claim 2 wherein a venturi is disposed in said first port, and the pump means includes a jet disposed adjacent one end of the venturi.

6. An incinerator comprising an insulated closed housing containing adjoining trash and afterburner chambers, a first wall between said chambers having a communicating opening between the chambers, said afterburner chamber comprising a volatiles combustion compartment and a flue separated by a second wall, said second wall having an opening adjacent one end for communication between adjacent end portions of said compartment and flue whereby exhaust from the compartment can flow into one end portion of the flue, an exhaust outlet havine one end penetrating the closed housing from the opposite end portion of the flue, and a vent box at the other end of the outlet, said vent box and outlet having means for passing exhaust outwardly from the flue and for simultaneously passing cool air inwardly to the housing.

7. An incinerator as set forth in claim 6 wherein said housing is disposed within and in spaced relation with a shell, and said exhaust outlet is enclosed within a conduit, and a passageway between the conduit and outlet, said passageway communicating at one end with the space between the housing and shell, and at the other end with the interior of said vent box.

8. An incinerator as set forth in claim 7 wherein said vent box is divided into two compartments in communicating relation respectively with said exhaust outlet and said passageway.

9. An incinerator as set forth in claim 8 wherein an air blower system is connected to the incinerator and includes means for directing air under pressure into the exhaust outlet.

10. An incinerator as set forth in claim 7 wherein an air blower system is connected to the incinerator and includes means for delivering air under pressure to the interior of the incinerator.

11. An incinerator comprising an insulated housing containing adjoining trash'and afterburner chambers, a first vertically extending wall between said chambers having spaced upper and lower ports therein, pump means in one of said chambers for circulating air through said chambers via said ports, said afterburner chamber comprising a volatiles combustion compartmerit and a flue separated by a second vertically extending wall, said second wall having an opening adjacent its lower end for communication between adjacent lower end portions of said compartment and flue whereby exhaust from the compartment can flow. into the lower end portion of the flue, and an exhaust outlet penetrating the housing from the upper end portion of the flue.

12. An incinerator as set forth in claim 11 wherein a burner is located at least partially within the volatiles combustion chamber adjacent one of said ports.

13. An incinerator as set forth in claim 11 wherein said pump means is located within the trash chamber 4 adjacent said upper port, and a blower means is connected with the pump means for circulating air through wall, a pair of spaced openings in said wall, means for introducing input air into said chambers through one of said openings, and means for varying;the rate of gas flow between the chambers through the other opening in response to changes in volume or pressure of gas generated by incinerator action on products within said chambers.

16. An incinerator as set forth in claim 15 wherein a burner is associated with one of said chambers for generating heat within the chambers, and said means for varying rate of gas flow operates in response to changes in volume or pressure of gases generated by action of said heat upon products in the other chamber.

.17. An incinerator as set forth in claim 16 wherein said means includes a venturi located in one of said ports, and a jet pump having an outlet end disposed adjacent one end of the venturi.

18. An incinerator as set forth in claim 17 wherein said wall is vertical, and said ports are disposed in vertically spaced relation in respective opposite upper and lower end portions of the wall. Q

19. An incinerator comprising a housing containing separate first and second chambers, communicating openings between said chambers, burner means in one of said chambers, means for injectingair' under pressure into one of said chambers and for creating circulation of gas between the chambers, means for maintaining the air injection ata predetermined level during the initial period of a burning cycle and for maintaining air injection during subsequent periods at a relatively higher level. v I

20. An incinerator comprising a housing, a primary chamber and an afterburner chamber within the housing, a wall between said chambers, ports in said wall, means for injecting air into one of said chambers for circulation between the chambers through the ports, means for producing a flame within the afterburner chamber for incineration of products in the primary chamber and of combustion products which flow from the primary chamber into the afterbumer chamber, and control means for maintaining said injection of air at a level lower than necessary to ignite the products in the primary chamber during an initial time cycle required to preheat the afterburner and to thereafter 

1. An incinerator comprising an insulated housing containing trash and afterburner chambers, a wall between said chambers, port means in said wall, and pump means having a portion located in one chamber for causing inspiration of gases therefrom through the port means into the other chamber and thence back into said one chamber through the port means.
 2. An incinerator comprising an insulated housing containing trash and afterburner chambers, a wall between said chambers, spaced first and second ports in said wall, and pump means having a portion located in said trash chamber adjacent said first port for introducing air under pressure through said first port and causing combustion products generated in the trash chamber to flow by inspiration therewith through the first port into the other chamber and thence back into said trash chamber through the second port.
 3. An incinerator as set forth in claim 2 wherein a burner is located at least partially within the afterburner chamber.
 4. An incinerator as set forth in claim 2 wherein said pump means is located in the trash chamber adjacent said first port.
 5. An incinerator as set forth in claim 2 wherein a venturi is disposed in said first port, and the pump means includes a jet disposed adjacent one end of the venturi.
 6. An incinerator comprising an insulated closed housing containing adjoining trash and afterburner chambers, a first wall between said chambers having a communicating opening between the chambers, said afterburner chamber comprising a volatiles combustion compartment and a flue separated by a second wall, said second wall having an opening adjacent one end for communication between adjacent end portions of said compartment and flue whereby exhaust from the compartment can flow into one end portion of the flue, an exhaust outlet havine one end penetrating the closed housing from the opposite end portion of the flue, and a vent box at the other end of the outlet, said vent box and outlet having means for passing exhaust outwardly from the flue and for simultaneously passing cool air inwardly to the housing.
 7. An incinerator as set forth in claim 6 wherein said housing is disposed within and in spaced relation with a shell, and said exhaust outlet is enclosed within a conduit, and a passageway between the conduit and outlet, said passageway communicating at one end with the space between the housing and shell, and at the other end with the interior of said vent box.
 8. An incinerator as set forth in claim 7 wherein said vent box is divided into two compartments in communicating relation respectively with said exhaust outlet and said passageway.
 9. An incinerator as set forth in claim 8 wherein an air blower system is connected to the incinerator and includes means for directing air under pressure into the exhaust outlet.
 10. An incinerator as set forth in claim 7 wherein an air blower system is connected to the incinerator and includes means for delivering air under pressure to the interior of the incinerator.
 11. An incinerator comprising an insulated housing containing adjoining trash and afterburner chambers, a first vertically extending wall between said chambers having spaced upper and lower ports therein, pump means in one of said chambers for circulating air through said chambers via said ports, said afterburner chamber comprising a volatiles combustion compartment and a flue separated by a second vertically extending wall, said second wall having an opening adjacent its lower end for communication between adjacent lower end portions of said compartment and flue whereby exhaust from the compartment can flow into the lower end portion of the flue, and an exhaust outlet penetrating the housing from the upper end portion of the flue.
 12. An incinerator as set forth in claim 11 wherein a burner is located at least partially within the volatiles combustion chamber adjacent one of said ports.
 13. An incinerator as set forth in claim 11 wherein said pump means is located within the trash chamber adjacent said upper port, and a blower means is connected with the pump means for circulating air through the chambers.
 14. An incinerator as set forth in claim 13 wherein a venturi is disposed in said first port, and the pump means includes a jet disposed adjacent one end of the venturi.
 15. An incinerator comprising an insulated housing containing first and second chambers separated by a wall, a pair of spaced openings in said wall, means for introducing input air into said chambers through one of said openings, and means for varying the rate of gas flow between the chambers through the other opening in response to changes in volume or pressure of gas generated by incinerator action on products within said chambers.
 16. An incinerator as set forth in claim 15 wherein a burner is associated with one of said chambers for generating heat within the chambers, and said means for varying rate of gas flow operates in response to changes in volume or pressure of gases generated by action of said heat upon products in the other chamber.
 17. An incinerator as set forth in claim 16 wherein said means includes a venturi located in one of said ports, and a jet pump having an outlet end disposed adjacent one end of the venturi.
 18. An incinerator as set forth in claim 17 wherein said wall is vertical, and said ports are disposed in vertically spaced relation in respective opposite upper and lower end portions of the wall.
 19. An incinerator comprising a housing containing separate first and second chambers, communicating openings between said chambers, burner means in one of said chambers, means for injecting air under pressure into one of said chambers and for creating circulation of gas between the chambers, means for maintaining the air injection at a predetermined level during the initial period of a burning cycle and for maintaining air injection during subsequent periods at a relatively higher level.
 20. An incinerator comprising a housing, a primary chamber and an afterburner chamber within the housing, a wall between said chambers, Ports in said wall, means for injecting air into one of said chambers for circulation between the chambers through the ports, means for producing a flame within the afterburner chamber for incineration of products in the primary chamber and of combustion products which flow from the primary chamber into the afterburner chamber, and control means for maintaining said injection of air at a level lower than necessary to ignite the products in the primary chamber during an initial time cycle required to preheat the afterburner and to thereafter raise said level to that required for ignition of said products.
 21. An incinerator as set forth in claim 20 wherein said control means comprises a time-controlled valve in said air injection means. 